Analog Switch Circuit for Signal Operation Beyond Power Rails
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Solution Overview
Problem
Conventional analog switches are limited by their signal range within regular power supply rails, and extending this range using internal charge pumps increases circuit complexity and DC power supply current.
Innovation Solution
The design extends the signal range beyond regular power rails without significant increases in circuit complexity or DC power supply current by using a configuration with P-channel and N-channel devices that include secondary voltage rails, allowing operation up to device breakdown voltage levels without distortion or undesirable currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If internal charge pumps are used to extend signal range beyond power rails, then signal range is improved, but circuit complexity increases significantly
Solution Approach 1:
The patent extracts the charge pump functionality from the internal circuitry and replaces it with external voltage sources. The signal range is extended by connecting the analog switch between external voltage rails rather than using internal charge pumps, thereby achieving extended signal range without the complexity of internal charge pump circuits.
Solution Approach 2:
The patent introduces external voltage sources as intermediary elements that provide the extended voltage rails. These external sources act as mediators between the power supply and the analog switch, enabling the switch to operate beyond the original power rail voltages without requiring complex internal voltage generation circuitry.
2Adaptability or versatility
If internal charge pumps are used to extend signal range, then signal range is improved, but DC power supply current increases significantly
Solution Approach 1:
The patent removes the energy-consuming charge pump circuits from the analog switch design. By using external voltage sources to provide the extended rails, the design eliminates the continuous DC current that would otherwise be required to operate internal charge pumps, thereby reducing overall power consumption.
Solution Approach 2:
The external voltage sources are responsible for providing their own power and maintaining their voltage levels independently. This self-service approach means the analog switch itself does not need to generate the extended voltage rails, avoiding the additional power consumption that would be required for internal voltage generation.
3Device complexity
If conventional analog switch configuration is used, then circuit complexity is low, but signal range is limited to power rails
Solution Approach 1:
The patent segments the voltage supply function from the switching function. The analog switch structure itself remains simple and unchanged, but it is connected to external voltage sources that provide the extended voltage rails. This segmentation allows the switch to operate beyond its original power rail limitations without complicating the switch circuitry.
Solution Approach 2:
The external voltage sources serve multiple functions: they provide the extended voltage rails for signal operation, they eliminate the need for internal charge pumps, and they reduce overall power consumption. This multi-functionality achieves signal range extension without proportionally increasing circuit complexity.
Data Source
AI summary
A switch circuit, which selectively couples first and second switch nodes together and which enables the first and second switch nodes to operate in an extended voltage range, includes a secondary voltage rail, a switch device, a body driver, a rail control switch, and a switch control circuit. The rail control switch clamps the secondary voltage rail to a primary voltage rail during normal voltage range operation, but otherwise releases the secondary voltage rail to float. The body driver clamps the body of the switch to the secondary voltage rail when turned on, and when turned off, forward biases to allow voltage of said secondary voltage rail to follow voltage of the switch nodes into the extended voltage range through the switch. The switch control circuit includes a latch circuit which ensures that the switch remains either turned on or turned off during extended voltage operation.